The international patent application WO 2009/141684 describes a display controller for use in a car application. The display controller generates a display signal representing an image to be displayed. Vehicle information and entertainment systems and consumer entertainment devices may employ sophisticated graphical schemes. A vehicle information and entertainment system may for instance display both safety relevant, such as the vehicle speed and engine temperature, and not safety relevant information, such as video or navigation information at the same time. During development of systems such display controllers need to be tested and the operation and functions need to be verified in a development process usually called debugging. Thereto such display controllers are provided with a debug interface to be coupled to a debug system, for example a computer having an appropriate hardware debug interface.
A drawback of such display controller devices is that the display signal needs to be analyzed during debugging. Thereto the actual contents of the display signal need to be captured. Capturing such high data rate signals requires substantial debugging hardware. Thereto such display controller may be provided with a writeback function to internally capture the display signal in a memory, which memory can be accessed by the debug system. However, such a memory needs to be relatively large and fast, and increases the complexity of the display controller.